LEC 10: Intertidal zones

why is the intertidal zone difficult for many organisms to survive in

since they have to work with terrestrial and marine environments almost simultaneously

what are the different intertidal zones called in order from highest/most terrestrial to lowest/most aquatic

* spray zone (get sprayed with water from waves every so often)
* upper intertidal (little water)
* mid intertidal (medium amount of water)
* lower intertidal (lots of water)
* subtidal

which organism do we find most of in the spray/splash zone?

a. lichen

b. crab

c. rough periwinkle

d. acorn barnacle

a

lichen represents a symbosis relationship between what?

fungi & photosynthetic algae/cyanobacteria

what is the predominant photosynthetic contributor to lichen

a. cyanobacterial

b. green algae

c. fungi

d. brown alage

b

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green algae makes up 90% of lichen

true or false: green algae is the only algae that can contribute to the symbiotic relationship of lichen (photosynthetic organism + fungi)

false: there are many photosynthetic organisms, and different types f algae that can form lichen relationships

what are the benefits of forming a lichen symbiotic relationship

* fungi will protect the green algae and cyanobacteria (roots/anchors them)
* so when they’re sprayed with water they don’t get washed into the sea
* the fungi can use the energy produced by cyanobacteria or green algae for their own needs as well

true or false: the symbiosis lichen is a mutualistic relationship

true

which of these organisms can be found in the upper intertidal zone

a. cyanobacteria

b. fiddler crab

c. rough periwinkle

d. all of the above

d

the upper intertidal zone is a more intense area of the intertidal area… how does cyanobacteria survive here? and how does it acquire nutrients

* they grow filamentous colonies
* they secrete a mucilaginous sheath (mucus sheath) around the colony to adhere to rocks

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* since it can adhere to the rock, when the tide comes in it can stay put while also collecting the nutrients it needs to survive (like water to do photosynthesis)

how do cyanobacteria in the intertidal area prevent photoinhibition, and avoid damage from too much sunlight

a UV-absorbing sheath pigment (scytonemin)

carotenoids → absorb excess excitation due to irradiance allowing them to be more efficient in photosynthetic processes at an upper point in the water column

where is the rough periwinkle located

a. subtidal zone

b. mid tidal

c. upper tidal

d. lower tidal

c

true or false: organisms such as cyanobacteria, fiddler crab and rough periwinkle can all be found on the lower intertidal zone

false: upper intertial

true or false: organisms such as algae, fungi and lichen can all be found on the spray zone

true

how does the rough periwinkle resist the strong tides

they secrete a mucus between the rock and the edge of their shell to seal themselves in at high tide

even in the upper tidal zone it is always possible to be submerged under water for long periods of time, possibly due to high tides… how do the rough periwinkle survive this

they switch to anaerobic metabolism

which statement about rough periwinkle is false:

a. they thrive more in anaerobic conditions than in aerobic conditions

b. they have lung-like organs that allow them to break on land like terrestrial snails

c. they have tongues called radula that they use to scrape off algae from the rocks and right into their esophagus

d. they secrete mucus to adhere to the rock in the upper intertidal zone

a

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they have lungs and breath air so they do better in aerobic conditions, but they are adapted to be under water for long periods of time by using anaerobic metabolism

what types of organisms can be found in the mid intertidal zone?

* mussels
* barnacles
* crustose algae
* acorn barnacle
* blue mussel
* dog whelk

in the mid intertidal zone what is the cyclical pattern of succession that we see with barnacles

* barnacles settle on the rock
* crustose algae invade the barnacles
* mussels overgrown the algae
* then due to strong waves mussels detach from the system

true or false: crustose algae can be found in the upper tidal zone

false: its found in the mid tidal zone

what does the “crustose” in crustose algae refer to

this is a way of adhering to the substrate it’s attached to and grows… the algae forms a crust by tightly adhering to a substrate

what is the name of the feet of the acorn barnacle

a. cirri

b. crustose

c. carotenoids

d. radula

a

what is a cirri?

what does it do?

what organism does it belong to?

* modified feet
* it extends into the water and filters zooplankton and detritus out of the water
* it belongs to the acorn barnacle

the acorn barnacle will only expose its cirri in the atmosphere and never in water … true or false

false… they only extend in water, when they are exposed to the atmosphere they retract and close up

define hermaphroditic

sexual reproduction BUT self fertilizing

* production of male and female gametes from one organism that get fertilized
* most intense form of inbreeding

acorn barnacles try to reproduce sexually through a long appendage that tries to probe other barnacles first but if it doesn’t work then it goes through hermaphrodiscism … true or false

true

true or false: in the larval stage of the acorn barnacle, it is planktonic

true

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it is floating in the open sea

define the allee effect

rate of population growth skewed based on population density

since there is a correlation between population size and mean individual fitness

what is dN/dt?

what is N?

what is K?

the change in population over the change in time

N= abundance/population size

K = carrying capacity

what does the allee effect have a correlation between

population size and mean fitness of an individual

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more individuals in a population the more fir each individual is

when we hit K what does this mean

it means the amount of deaths = the amount of births

we are at the rate of replacement!!

when there is an allee effect what occurs in the graph?

skewedness

how are acorn barnacles affected by the allee effect?

* when barnacles are close in proximity this is advantageous for them


* they can trap water, share nutrients, protect each other, etc
* and with this they can grow their population more readily
* with bigger population size, we increase individual fitness as well

what are examples of density dependent factors

space

food/resources

competition

predation

how do blue mussels survive in the mid intertidal zone

they have a bearded filament

very strong sticky glue like material the produce

can stick to even non-sticky material

which of these are filter feeders (select all that apply):

a. blue mussel

b. whale shark

c. acorn barnicals

d. rought periwinkle

a,b,c

how do blue mussels survive the strong tides of the mid intertidal region

with byssal threads that attach to rock

what is a bi-phasic life cycle in terms of blue mussel

* planktonic larval stage
* then meta metamorphosizes into a sessile adult form

how do blue mussels exhibit an allee effect

through broadcast spawning:

* they release a whole lot of gametes into the water
* “shotgunning” gametes out there in hopes of that it will reach other gametes to reproduce
* SO when mussels are close in proximity (in a group together) the higher the likelihood chance of sexual reproduction

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* with increased population size we have increased fitness!

true or false: blue mussels are foundational species, they filter out any heavy metals or contaminants, and improve water quality… they improve their local environment and have a big effect on biodiversity

true

which of these respire through gills

a. rough periwinkle

b. dog whelk

c. blue mussle

d. acorn barnical

b

how does the dog whelk feed?

boring hole shells of mussels and barnacles using their radula

they excrete juices into the mussel and slurp out their insides

which two organisms have a radula for feeding

dog whelk and rough periwinkle

what reproducive methods is the sea star capable of?

* sequential/simultaneous hermaphroditism
* fragmentation (by the red scaly sea star)

which of these species is a keystone species, select all that apply:

a. acorn barnical

b. sea star

c. blue mussel

d. antarctic krill

b,c,d

in an experiment where sea starts were hand picked out of an area and then the area was observed over a year, what was determined?

there was less biodiversity after the year

went from 16 down to 8 different species in that area

sea stars are essential to biodiversity

removal of sea stars decreases biodiversity

true or false: sea stars are key stone predators

true!

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they eat anything

they are generalists

what type of macroalgae are each other these

chlorophyta

ochrophyta

rhodophyta

chlorophyta = green algae

ochrophyta = brown algae

rhodophyta = red algae

why is chlorophyta green

because chlorophyll a,b,c all absorb blue and reflect green

why is ochrophyta brown

becasue fucoxanthin (carotenoid) abosrobs blue and reflects orange/reds (to get brown)

why is rhodophyta red

b/c phycocyanin absorbs green and reflects red

what is the name of the macroalgae structure that anchors the algae to the ground

holdfast

true or false: the holdfast is a root system that provides macroalgae with the nutrients that it needs to survive

false!: the holdfast is only to fasten the macroalgae to a substrate and holds it in place and does not get washed away

* NO vascularization
* NO nutrient movement

what does the stipe of the macroalgae do?

this is a central, stem-like structure

* no true vascular tissue

true or false: the blades of macroalgae have photosynthetic potential

true

when comparing a terrestrial plant and a macroalgae, what different do we see microscopically in attribution to photosynthesis

we see chloroplasts on the top and bottom of macroalgae

and only see chloroplasts on the top of terrestrial plants → since it moves around a lot (fronds whipping around) in the water this allows for more photosynthesis

holopelagic vs. sessile

holopelagic = organism that floats along the ocean surface for its whole life and never attaches to anything

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sessile = organism that is anchored at the base

seaweed is typically found in the upper intertidal zone … true or false

false: lower intertidal zone

how can the seaweed have a negative effect on bivalves such as barnicals in high density

* their fronts act as whips and can damage the cirri of the barnacles
* in high densities it can overrun other organisms in the area

how can seaweed be benefial, when in low densities

* protection
* habitat for whelks too
* retains water in times of low tide

where are bladder wracks found

lower intertidal zone

how do the bladder wrack have unique pneumatocyts?

their gas bladders are at the ends of the blades and hold gametes in them to be releases

if someone was to develop goiter, what can be eaten to treat it? why?

bladder wrack (seaweed) since it has a high concentration of iodine

how does the bladder wrack deter predators?

produces phenols (carbolic acid) and tannins to deter mollusks and sea urchins